The present invention relates to a dehumidifying apparatus, and more particularly to a dehumidifying apparatus having a high moisture removal.
As shown in FIG. 17, there has heretofore been available a dehumidifying apparatus 11 having a compressor 1 for compressing a refrigerant C, a condenser 2 for condensing the compressed refrigerant C to heat process air A, an evaporator 3 for depressurizing the condensed refrigerant C with an expansion valve 5 and evaporating the refrigerant to cool the process air A to a temperature equal to or lower than its dew point. The evaporator 3 cools the process air A from an air-conditioned space 10 to a temperature equal to or lower than its dew point to remove moisture from the process air A, the condenser 2 heats the process air A which has been cooled to a temperature equal to or lower than its dew point, and the heated process air A is supplied to the air-conditioned space 10. With the illustrated dehumidifying apparatus 11, a heat pump HP is constituted by the compressor 1, the condenser 2, the expansion valve 5, and the evaporator 3. The heat pump HP pumps heat from the process air A which flows through the evaporator 3 into the process air A which flows through the condenser 2.
The conventional dehumidifying apparatus 11 having the heat pump HP cannot supply dry air having an absolute humidity of 4 g/kgDA or lower. The reason is that since the operating temperature of the evaporator 3 in the heat pump HP is equal to or lower than the freezing point, the removed moisture is deposited as frost on the heat transfer surface to inhibit the heat transfer, and hence the apparatus cannot continuously be operated.
It is therefore an object of the present invention to provide a dehumidifying apparatus which can prevent moisture removed from air from being deposited as frost on a heat transfer surface of an evaporator in a heat pump to continuously supply dry air having an absolute humidity of 4 g/kgDA or lower.
To achieve the above object, according to an aspect of the present invention, as shown in FIG. 1, for example, there is provided a dehumidifying apparatus comprising: a moisture adsorbing device 103 for removing moisture from process air A and for being regenerated by desorbing moisture therefrom with regeneration air B; and a heat pump HP1 having a condenser 220 for condensing a refrigerant C to heat said regeneration air B at the upstream side of said moisture adsorbing device 103, an evaporator 210 for evaporating said refrigerant C to cool said regeneration air B to a temperature equal to or lower than its dew point at the downstream side of said moisture adsorbing device 103, a pressurizer 260 for raising a pressure of said refrigerant C evaporated by said evaporator 210 and delivering said refrigerant C to said condenser 220, and a first heat exchanger 300 for exchanging heat between said regeneration air B flowing between said moisture adsorbing device 103 and said evaporator 210 and the regeneration air B flowing between said evaporator 210 and said condenser 220; wherein said regeneration air B is used in circulation.
With the above arrangement, since the dehumidifying apparatus has the condenser, the evaporator, and the first heat exchanger, the regeneration air is circulated such that it is heated by the condenser, regenerates the moisture adsorbing device to increase the amount of moisture contained in the regeneration air, is cooled by the first heat exchanger, is cooled and condensed by the evaporator to reduce the amount of moisture contained in the regeneration air, and is heated by the first heat exchanger. When the regeneration air is cooled by the first heat exchanger, the moisture thereof may partly be condensed, reducing the amount of moisture contained in the regeneration air. The regeneration air is cooled (precooled) by the first heat exchanger prior to cooling in the evaporator, and is heated (preheated) by the heat exchanger after cooling by the evaporator. Therefore, the dehumidifying apparatus can be operated at a low sensible heat factor.
Since the moisture of the process air is adsorbed by the moisture adsorbing device, the humidity of the process air is greatly reduced, and hence dry air can be supplied. The expression that the regeneration air is used in circulation means that after having regenerated the moisture adsorbing device, e.g., the desiccant of a desiccant wheel, the regeneration air flows a circulating circuit so that most of the regeneration air can be used again as regeneration air, without being discharged directly into the atmosphere (no regeneration air may be discharged into the atmosphere, or part of regeneration air may be discharged into the atmosphere).
In the first heat exchanger, the refrigerant is evaporated and condensed typically under an intermediate pressure between the condensing pressure in the condenser and the evaporating pressure in the evaporator.
In the dehumidifying apparatus, the first heat exchanger 300 may comprise a thin pipe group connecting the condenser 220 and the evaporator 210 to each other, for passing the refrigerant therethrough; wherein the thin pipe group may be arranged so as to introduce the refrigerant condensed by the condenser 220 to the evaporator 210 and also to bring said refrigerant into alternate contact with the regeneration air flowing between the moisture adsorbing device 103 and the evaporator 210 and the regeneration air flowing between the evaporator 210 and the condenser 220.
With the above arrangement, since the thin pipe group into which the refrigerant is introduced is brought into alternate contact with the regeneration air flowing between the moisture adsorbing device and the evaporator and the regeneration air flowing between the evaporator and the condenser, heat exchange between these two flows of the regeneration air can be performed by the refrigerant. The connection between the condenser and the evaporator includes indirectly connecting the condenser and the evaporator with a pipe, a pipe joint, or the like.
In the dehumidifying apparatus, as shown in FIG. 1, for example, the first heat exchanger 300 may have a first compartment 310 for passing the regeneration air between the moisture adsorbing device 103 and the evaporator 210, and a second compartment 320 for passing the regeneration air between the evaporator 210 and the condenser 220, the thin pipe group being connected to the condenser 220 through a first restriction 330, extending alternately through the first compartment 310 and the second compartment 320 repeatedly, and then being connected to the evaporator 210 through a second restriction 250.
With the above arrangement, since the dehumidifying apparatus has the first restriction and the second restriction, while the refrigerant is passing through the first restriction and the second restriction, the refrigerant develops a pressure drop across each of the first restriction and the second restriction. The refrigerant passing through the first compartment is evaporated and the refrigerant passing through the second compartment is condensed under an intermediate pressure between the condensing pressure of the refrigerant in the condenser and the evaporating pressure of the refrigerant in the evaporator. Therefore, the heat exchanger acts as an economizer, and the coefficient of performance (COP) of the heat pump is increased.
As shown in FIG. 13, for example, the dehumidifying apparatus may have a plurality of thin pipe groups 51 (52, 53) connected to the condenser 220 through first restrictions 331a (332a, 333a) and alternatively extending through the first compartment 310 and the second compartment 320 repeatedly and then connected to the evaporator 210 through corresponding second restrictions 331b (332b, 333b), and a plurality of combinations of the first restrictions 331a, 332a, 333a and the second restrictions 331b, 332b, 333b which correspond respectively tothe thin pipe groups 51, 52, 53. As shown in FIG. 13, the first compartment 310 and the second compartment 320 should preferably be arranged such that the regeneration air flows as counterflows in the respective compartments 310, 320.
In the dehumidifying apparatus, as shown in FIG. 8, for example, the first compartment 310 and the second compartment 320 may be arranged such that the regeneration air flows as counterflows in the respective compartments 310, 320; and the thin pipe groups in the first compartment 310 and the second compartment 320 may have at least a pair of a first compartment extending portion 251B and a second compartment extending portion 252B in a first plane PB which is substantially perpendicular to the flows of the regeneration air, at least a pair of a first compartment extending portion 251C and a second compartment extending portions 252C in a second plane PC, different from the first plane PB, which is substantially perpendicular to the flows of the regeneration air, and an intermediate restriction 331 disposed in a transitional location from the first plane PB to the second plane PC.
With the above arrangement, from the viewpoint of heat exchange between the flows of the regeneration air, a high heat exchange efficiency is achieved because heat exchange can be performed between counterflows. The thin pipe groups have at least a pair of a first compartment extending portion and a second compartment extending portion in the first plane to form a pair of refrigerant paths, and at least a pair of a first compartment extending portion and a second compartment extending portion in the second plane, different from the first plane, which is substantially perpendicular to the flows of the regeneration air, to form a pair of refrigerant paths. Therefore, the heat exchanger can be constructed in a small compact size as a whole. Since the thin pipe groups also have an intermediate restriction disposed in a transitional location from the first plane to the second plane, the pressure of evaporation or condensation in the first and second compartment extending portions in the second plane can be of a value lower than the pressure of evaporation or condensation in the first and second compartment extending portions in the first plane. Accordingly, the heat exchange between the flows of the regeneration air flowing through the respective compartments can be made similar to counterflow heat exchange, thus increasing the heat exchange efficiency. The first plane and the second plane typically comprise rectangular planes.
As shown in FIG. 1, for example, the dehumidifying apparatus may have a second heat exchanger 340 disposed in the passage of the regeneration air used in circulation, for exchanging heat between the regeneration air and another fluid.
With the above arrangement, the second heat exchanger is capable of exchanging heat between the regeneration air and the other fluid for cooling or heating the regeneration air. The second heat exchanger typically cools the regeneration air.
As shown in FIG. 6, for example, the second heat exchanger 340a comprises a second thin pipe group connecting the condenser 220 and the first heat exchanger 300 to each other, for passing the refrigerant therethrough, and the second thin pipe group is arranged so as to introduce the refrigerant condensed by the condenser 220 to the first heat exchanger 300 and also to bring the refrigerant into alternate contact with the regeneration air flowing between the moisture adsorbing device 103 and the first heat exchanger 300 and the other fluid.
With the above arrangement, the second heat exchanger is capable of exchanging heat between the regeneration air and the other fluid via the refrigerant.
The other fluid should preferably comprise external air. With this arrangement, the excessive amount of heat of the regeneration air can be discharged into external air which is an almost unlimited source of heat.
The present application is based on Japanese patent application No. 2000-025811 filed on Feb. 3, 2000, which is incorporated herein as part of the disclosure of the present application.
The present invention can more fully be understood based on the following detailed description. Further applications of the present invention will become more apparent from the following detailed description. However, the following detailed description and specific examples will be described as preferred embodiments only for the purpose of explaining the present invention. It is evident to a person skilled in the art that various changes and modifications can be made to the embodiments in the following detailed description within the spirit and scope of the present invention.
The applicant has no intention to dedicate any of the embodiments described below to the public, and any of the disclosed modifications and alternatives which may not be included in the scope of the claims constitutes part of the invention under the doctrine of equivalent.